A fluororesin coating material is a coating material having a fluoropolymer incorporated, and since it is excellent in weather resistance and ultraviolet light resistance, it has been used in recent years as a maintenance free high performance coating material in a wide range of applications to e.g. tall buildings, large structures, ships, vehicles, houses, bridges, etc. Especially, a fluoropolymer containing hydrolyzable silyl groups is useful as a fluororesin for an environment-friendly coating material which is less influential over the global environment, since an organosilane type curing agent easy to handle can be used as a curing agent. Further, in a case where a fluoropolymer containing hydrolyzable silyl groups is used as a raw material for a fluororesin coating material, the physical properties of the coating film, such as weather resistance, hardness, water repellency, etc. are improved, and thus, such is useful also from the viewpoint of high functionality of the coating film.
However, the hydrolyzable silyl group-containing fluoropolymer is likely to undergo gelation as the internal crosslinking reaction of hydrolyzable silyl groups is likely to readily proceed by e.g. moisture in air, whereby it has been very difficult to secure a practically sufficient pot life and storage stability.
As a process for producing a hydrolyzable silyl group-containing fluoropolymer, processes have been proposed wherein an alkoxysilane compound having an isocyanate group is reacted to hydroxy groups of a hydroxy group-containing fluoropolymer under such a condition that dibutyltin dilaurate as an organic metal catalyst is present in an amount of from 25 to 35 ppm by mass of tin metal single substance based on the hydroxy group-containing fluoropolymer, or no such an organic metal catalyst is present (Patent Documents 1 to 3). However, in each of such processes, it has been difficult to obtain a hydrolyzable silyl group-containing fluoropolymer which is excellent in storage stability and has a sufficient pot life.